This invention relates to a freeze-concentrating apparatus for an aqueous solution, an ice pillar producing apparatus and a freeze-concentrating method for an aqueous solution, which are particularly used for concentration of an aqueous solution such as beverage, alcohol, a medicament and for disposal for turning industrial waste water or seawater into fresh water.
In general, a freeze-concentrating method is a method of concentrating an aqueous solution by cooling a target aqueous solution, freezing water within the aqueous solution to obtain an ice, extracting the ice by solid-liquid separation. Accordingly, the method is suitable for concentrating an aqueous solution of which solute is liable to be degraded and a beverage of which aroma is liable to fade under a high temperature.
Also, the extracted ice in the above freeze-concentrating method can be utilized as a regenerative material, and the method can be applied to a case for turning seawater into fresh water.
Problems to be Solved
In the above freeze-concentrating method, continuous operation is required for industrial utilization. However, enablement of the continuous operation in a conventional freeze-concentrating apparatus requires freezing operation and the like, which increases the size of the apparatus itself and requires considerable facility investment.
Further, in case where a target liquid is different in kind of solute or concentration, it is difficult for the conventional freeze-concentrating apparatus to perform adjustment according to the target liquid.
On the other hand, in the above freeze-concentrating method, extraction of ice crystals under a state that a solution adheres to the surface of the ice crystals decreases the concentration efficiency. For this reason, less surface area (specific surface) of the ice crystals is preferable. To reduce the specific surface of the ice crystals, it is needed to obtain spherical ice crystals having large diameters.
Accordingly, in the above freeze-concentrating method, it is required for the continuous operation to convey the ice crystals in a state of fluid, namely, to convey a suspension containing the ice crystals in a state of slurry. Further, there is another problem how to make spherical ice crystals having large diameters in the suspension.
In so doing, as ice producing means for producing a suspension containing an ice to be used for freeze concentration, it is general to produce an ice by condensing water on the surface of a cooled drum or the inner surface of a cylinder, then scraping the thus produced ice.
However, ice crystals obtained by this ice producing means are flaky. For this reason, a maturing tank is separately used as means for producing and growing the ice crystals, and the ice crystal is stirred under a given temperature condition to grow the ice crystals to be spherical and large. Therefore, the treated aqueous solution of which amount corresponds to the capacity and residence time of the maturing tank is always required in addition to a required amount thereof for the ice production. As a result, the apparatus is large sized.
Moreover, for the above ice producing means, there is a method of producing an ice in quasi-criticality by excessive cooling, which is used for regenerating cooling/heating energy and the like for air conditioning. According to this ice producing means, a suspension containing ice crystals in nearly spherical shape can be obtained. However, the ice crystals obtained by this ice producing means have extremely small grain diameters, which means difficultly in solid-liquid separation. Since there is no conventional method for effectively growing the ice crystals, this ice producing means has not been applied to the freeze-concentrating method.
The present invention has been made in view to the above problems and its conception is that even flaky ice crystal or spherical but small ice crystal can be used for freeze-concentration regardless of an ice producing method if the ice crystals can be accumulated in a short period of time without using a special maturing tank and can be grown in the spherical shape. Accordingly, the object of the present invention is to grow ice crystals to be large and spherical in a suspension, while reducing the entire size of an apparatus.
Summary of the Invention
The inventors of the present invention have found that spherical ice crystals having large grain diameters can be obtained in such a manner that a suspension containing ice crystals is produced by cooling an aqueous solution, a liquid component is separated and discharged from the suspension to increase the ratio of the ice crystals in the suspension, and the ice crystals are grown to produce an ice pillar. The inventors have further found that a concentrated solution can be obtained in such a manner that, for example, the thus obtained ice pillar is inserted in a column filter, cold water is injected into one end of the column filter to push out a concentrated solution in the ice crystals of the ice pillar from the other end of the column filter. In consequence, the present invention has been achieved.
Means of Solving the Problems
In detail, first solving means is directed to a freeze-concentrating apparatus for an aqueous solution. This solving means comprises ice producing means, having a heat exchanger for cooling, for continuously producing a suspension containing ice crystals by cooling an aqueous solution by the heat exchanger for cooling. Further, it comprises ice pillar producing means, to which the suspension produced by the ice producing means is supplied, for separating and discharging a liquid component from the suspension to increase the ratio of the ice crystals and for producing a column-shaped ice cake by growing the ice crystals. In addition, there is provided separating means for taking out a concentrated solution from the ice pillar produced by the ice pillar producing means.
A second solving means comprises, in the first solving means, ice pillar cutting/conveying means for cutting the ice cake produced by the ice pillar producing means into an ice pillar of a given length and for conveying the ice pillar to the separating means.
In third solving means, the ice producing means in the first or second solving means includes a stirring mechanism for stirring the aqueous solution flowing to a cooling cylinder serving as the heat exchanger for cooling or a scraping blade mechanism for scraping an ice generated on the surface of a cooling cylinder serving as the heat exchanger for cooling.
In fourth solving means, the ice pillar producing means in any one of the first through to third solving means includes a producing cylinder to which the suspension is supplied, and a filter, attached to a part of the side wall of the producing cylinder, for separating and discharging the liquid component from the suspension. In addition, the producing cylinder has at the inside thereof an accumulating chamber for producing a column-shaped ice cake by accumulating the suspension, fusing the ice crystals in the suspension by at least one of pressure application and the weight of itself, and growing the ice crystals.
In fifth solving means, the producing cylinder in the fourth solving means includes a rectification plate, in which a plurality of holes is formed, for rectifying the suspension. Further, the accumulating chamber is divided into an upper chamber and a lower chamber by the rectification plate. In addition, an outer cylinder is provided outside of the producing cylinder for receiving the liquid component discharged from the producing cylinder.
In sixth solving means, the separating means in any one of the first through to fifth means includes a column filter to which the ice pillar is inserted, and a cold water injecting mechanism, having a head part adhered to and caught by the column filter, for substituting the concentrated solution in the ice pillar for cold water by injecting cold water into the column filter through the head part to take out the concentrated solution.
In seventh solving means, the separating means in any one of the first through to fifth solving means includes a column filter to which the ice pillar is inserted, and a vacuum pump, connected with the lower part of the column filter, for taking out the concentrated solution in the ice pillar by applying a negative pressure to the column filter.
In eight solving means, the separating means in any one of the first through to fifth solving means includes a centrifuge, having a rotary cylinder for crushing adequately and accommodating the ice cake produced by the ice pillar producing means, for centrifugally separating to take out the concentrated solution in the ice cake by rotating the rotary cylinder.
Ninth solving means is directed to an ice pillar producing apparatus. This solving means comprises a producing cylinder to which a suspension containing ice crystals is supplied. Further comprised is a filter, attached to a part of the side wall of the producing cylinder, for separating and discharging a liquid component from the suspension. In addition, the producing cylinder includes at the inside thereof an accumulation chamber for producing a column-shaped ice cake by accumulating the suspension, fusing the ice crystals in the suspension by at least one of pressure application and the weight of itself, and growing the ice crystals.
Also, in tenth solving means, the producing cylinder in the ninth solving means includes a rectification plate, in which a plurality of holes are formed, for rectifying the suspension. Further, the accumulation chamber is divided into an upper chamber and a lower chamber by the rectification plate. In addition, an outer cylinder is provided outside the producing cylinder for receiving the liquid component discharged from the producing cylinder.
Further, eleventh solving means is directed to a method of freeze-concentrating an aqueous solution. In this solving means, an aqueous solution is cooled first by a heat exchanger for cooling of ice producing means, and a suspension containing ice crystals is continuously produced. Then, the suspension produced by the ice producing means is supplied to the ice pillar producing means to produce a column-shaped ice cake by separating and discharging a liquid component from the suspension to increase the ratio of the ice crystals, and growing the ice crystals. Subsequently, the ice cake produced by the ice pillar producing means is cut into an ice pillar of a given length and is conveyed and inserted to a column filter of separating means by ice pillar cutting/conveying means. Thereafter, cold water is injected or infused into the separating means to take out the concentrated solution in the ice crystals in the ice pillar.
Operation
According to the above-prescribed limitations in the invention, the cooling cylinder serving as the heat exchanger for cooling is cooled by driving the ice producing means and the aqueous solution is supplied to the ice producing means. In the cooling cylinder, the aqueous solution is stirred by, for example, a stirring member to become the suspension containing the ice crystals, then is flown into the ice pillar producing means.
The suspension is flown into the producing cylinder of the ice pillar producing means to be stirred by the flow thereof. For example, the suspension flows through the holes of the rectification plate, so that the ice crystals are more evenly dispersed. Then, the ice crystals float up in the suspension.
Since the liquid component is discharged from the suspension in the producing cylinder, the ice crystals are deposited and are compressed by receiving the weights of the suspension and the ice cake, thereby the ice crystals are fused and grown. As a result, the ice crystals which are solidified to be the ice cake are pushed upward.
Thereafter, the ice cake is, for example, cut into the ice pillar of the given length then is conveyed to the column filter of the separating means by the ice cutting/conveying means. In the separating means, for example, the cold water is injected into the column filter to substitute the concentrated solution in the ice pillar for the cold water, so as to be discharged out from the column filter.
The concentrated solution may be utilized directly or condensed again, and the ice pillar after the substitution is reused as a thermal source for cooling, and the like.
Effects
According to the present invention, the suspension produced by the ice producing means contains the ice crystals of a high ratio, the ice crystals are grown to produce the column-shaped ice cake, and the concentrated solution is taken out from the ice pillar of the given length into which the ice cake is cut, thereby achieving continuous drive of freeze concentration. Additionally, size reduction of the device itself and cost reduction for facility investment can be contemplated.
Also, even if a target liquid is different in kind of solute or concentration, adequate adjustment can be easily performed in accordance with the liquid.
Since the ice crystals in the suspension produced by the ice producing means can be made large and spherical by the ice pillar producing means, the ice crystals, which are produced regardless of an ice producing method, can be used for freeze concentration. This attains great enhancement of concentration efficiency.
Consequently, the present invention is useful in concentration of fruit juice, grape juice, and the like, for concentration of pharmaceutical material, for turning seawater into fresh water for shipping and for remote islands, and for disposal of industrial waste water.
In addition, according to the ninth and tenth solving means, the thus produced ice pillar may be used as food in a sherbet state with the use of wine. Especially, food having novel taste such as a stuffing in a dumpling is obtained, instead of frosty food such as conventional food in a sherbet state.